The cerebellum has a critical role in motor coordination, balance and controlling eye sacchades, with recent evidence highlighting a role in feed-forward learning, visuo-spatial memory, attention, language, and other higher cognitive functions. Importantly, cerebellar pathology and dysfunction have been linked to developmental diseases such as autism and ADHD. While mouse models of such complex disorders have provided critical insights, mouse genetic models do not always model human disease phenotypes. There is therefore a critical need for a human model system to study cerebellar development and dysfunction. Excitingly, it is now possible to create human model systems of the central nervous system through the use of human pluripotent stem cells (hPSCs). While hPSC-based human model systems have been developed for disorders such as Parkinson's disease and Amyotrophic Lateral Sclerosis through the differentiation of dopaminergic or motor neuron subtypes, protocols for the generation of specific cerebellar neurons are lacking. The proposed research aims to develop methods to differentiate hPSCs into the two primary neurons of the cerebellum, the granule cell (GC) and the Purkinje cell (PC), and thoroughly characterize resulting cells. To assess gene expression, a novel genetic tool, the bacTRAP, will be employed to isolate translating mRNA specifically from EGFP-tagged GCs or PCs within a heterogeneous culture. Following RNA sequencing, results will be compared to datasets of various developmental stages of native mouse GCs and PCs already obtained in the lab. To assess physiology, basic membrane properties as well as GC and PC specific currents will be measured in vitro. To assess the ability to integrate into the cerebellar circuit, we will adapt methods we reported for mES cells to implant hPSC-derived GCs and PCs into the neonatal mouse cerebellum. Clarity or ClearT2 tissue clearing methods and novel whole brain imaging techniques will allow imaging of the development and integration of implanted neurons within the mouse cerebellar circuit. These assays will provide a detailed analysis of hPSC-derived GC and PC gene expression and functional capacity, against which patient-hPSC derived cerebellar neurons, as well as other neural subtypes, can be assessed. The Hatten lab has carried out seminal studies on cerebellar development and neuronal migration. In preliminary work, the Hatten lab has generated protocols for the differentiation of mouse ES cells into cerebellar neurons and utilized bacTRAP to obtain gene expression datasets of native mouse GCs and PCs. Importantly; we have adapted these differentiation protocols to hPSCs, generating definitive human GCs and PCs for the first time. The proposed research aims to refine these protocols to generate mature neurons, and to thoroughly characterize them through gene expression profiling, electrophysiology, and integration capacity into the mouse cerebellar circuit following implantation. These studies will create a critical new human model system of cerebellar development and dysfunction.